The present invention generally relates to a method of making a semiconductor apparatus without a parasitic junction.
A threefold diffusing system as shown in FIG. 20 in the conventionally used semiconductor apparatus had much diffusion of a P.sup.- region, the concentration of the P.sup.- region was higher than N.sup.- region and a part of the P.sup.- region had to be made lower in concentration, with a defect that series resistance of a collector became larger. The larger concentration ratio of the base and the emitter was hard to obtain as no room was provided in an impurity profile. As the injecting efficiency of the emitter could not be raised, the gain was small.
In such conventional P-WELL system as shown in FIG. 21, the resistance of a P.sup.+ region could be lowered, but the concentration of a flush P region was hard to be made larger than a flush N.sup.+ region. The series resistance of the collector was adapted to be lowered with the use of the layer of UP-DOWN ISO. As a P (collector) region was in contact against the flush N.sup.+ region, the withstand pressure of the collector could not be made high with a defect that the area became larger.
Such conventional SUB-PNP system as in FIG. 22 was the same as the P-WELL system of FIG. 21 except for the collector of the PNP. Although the series of the collector could be lowered by a portion where the flush layer of N.sup.+ was not provided, with a defect that the collector potential could not be obtained freely as the collector was short in circuit with the SUB.
The above described FIG. 11, FIG. 12 had a defect that parasitic effects were caused if the bias of the surrounding N.sup.- EPI was made better. Although FIG. 20, FIG. 21, FIG. 22 could have the NPN provided jointly, difference was considerable in peculiar characters so that NPN / PNP mutually supplementary type was hard to obtained.